Aquaponics: An Efficient Way to Feed Ourselves?

Aquaponics is always a hot topic here on TreeHugger - especially if you dare to ask, as I did last week, whether aquaponics is cruel. During the course of the discussion that ensued, another interesting point came up - how efficient is aquaponics really? Can it really help reduce the impact of growing food and raising animal proteins, or are there unsee impacts occurring elsewhere? The answer, as usual, is that it depends on what you raise and how you raise it...We already know from projects like Will Allen's Growing Power that urban aquaponics can help grow a huge amount of both vegetables and fish in some tiny spaces. But as commenter Landanger questioned (along with a not-so-subtle argument for vegetarianism), what about the inputs for the fish:

But beyond the fact that you are quibbling over whether keeping the animal in a confined space is cruel before murdering it and eating its remains, which is a stupid discussion, how come the efficiency of fish farming isnt being discussed here? What are you feeding the fish, and how much energy is being expended to produce the food the fish is being given?

This is an important point - after all, commercial fish farming often uses fish as the feedstock - trawling up huge amounts of species not consumed by humans, grinding them up, and feeding them to more palatable species. Undoubtedly, if that's what ends up as the input for an aquaponics system, then the whole efficiency argument is somewhat flawed.

However, most aquaponics enthusiasts favor tilapia - an omnivorous fish that apparently can thrive on duckweed alone, although they are often fed commercial fish feed too. So if we can feed the fish on plant-based foods that would not otherwise be fit for human consumption - especially if those foods can be grown in ponds with minimal input from us, then we are on our way toward a sustainable system.

It's also important to note that fish farming carries an inherent efficiency benefit - compared to land-based livestock farming at least - in that fish can use vertical space in a way that a cow, for example, can't. They also don't need to support themselves against gravity and therefore use less energy - meaning that for each calorie you put in, more is converted to meat not heat. This benefit is further compunded by the fact that fish are cold blooded, and that water changes temperature less rapidly than air, so less feed is also wasted in regulating body temperatures.

So, as far as I can tell at least, aquaponics has a huge potential for more sustainable food production - both as a greener way to produce meat, and as a more efficient way to farm your vegetables. Of course none of that will counter Landanger's other argument about "murdering and eating" animals - but that's a debate that is likely to rage for some time to come.